Growth and development follow a cycle that is patterned and predictable. For the most part there are four stages to the process: start, grow, mature and decline. Each stage in the growth curve takes approximately two years. The shocking reality is that without maintenance the advances made over six years can be lost in just over two.
To avoid backslide you will want to think in terms of a three to five year cycle when time is dedicated specifically to setting new goals and establishing new priorities. This cycle also helps maintain a sense of stability while continuing to incorporate new thinking.